Add option to specify a registry

PR #9 from @raaymax

index.js

@@ -18,6 +18,7 @@ const dockerCommand = process.env.DOCKER || '/usr/bin/docker'
 const token = process.env.TOKEN || ''
 const username = process.env.USERNAME || ''
 const password = process.env.PASSWORD || ''
+const registry = process.env.REGISTRY || ''
 
 app.use(bodyParser.json())
 app.use(bodyParser.urlencoded({ extended: true }))
@@ -39,7 +40,7 @@ app.post('/webhook/:token', (req, res) => {
   const service = services[image].service
 
   // Make sure we are logged in to be able to pull the image
-  child_process.exec(`${dockerCommand} login -u "${username}" -p "${password}"`,
+  child_process.exec(`${dockerCommand} login -u "${username}" -p "${password}" ${registry}`,
     (error, stdout, stderr) => {
       if (error) return console.error(error)
 
@@ -63,4 +64,4 @@ app.all('*', (req, res) => {
 app.listen(process.env.PORT, err => {
   if (err) throw err
   console.log(`Listening for webhooks on http://localhost:${process.env.PORT}/webhook/${token}`)
-})
+})